A Northern Alliance rebel clutches a rocket-propelled grenade captured from the Taliban outside Kabul.

KOTAL KHAIRKHANA, Afghanistan - Taliban military forces deserted the capital of Kabul at dawn today after the opposition, aided by well-coordinated U.S. air strikes, overran Taliban entrenchments north of the city with stunning ease.

Some Northern Alliance forces began moving into the capital with pickup trucks loaded with soldiers armed with rifles and rocket launchers. There was no shooting as the opposition forces took over a military barracks that only hours before had been in Taliban hands.

The loss of the capital, coupled with the opposition's conquest of most of northern Afghanistan in the last four days after more than a month of U.S. air strikes, dramatically weakens the Taliban's grip on power in the nation.

The Northern Alliance now controls nearly 50 percent of the country, up from the 10 percent it held late last week before it took the city of Mazar-e Sharif and started rolling up victories across the northern half of the country. The province of Kunduz and a city in it by the same name are reportedly the last remaining strongholds of the Taliban in the north.

Gen. Haji Almas, the commander of opposition forces in Rabat, said Northern Alliance soldiers were waiting for their police forces to secure the capital. "We are very excited. We have captured the center of Afghanistan," he said.

Scores of people were seen leaving the city today. Among them was Abdullah, 23 and unemployed, who said, "All of the people of Kabul are happy. The Taliban left quickly overnight."

Villages leading into the city were devastated by the fighting, with deep bomb craters throughout the landscape. The fleeing Taliban fighters left some of their military equipment behind, and it was being scavenged by Northern Alliance fighters.

Dr. Abdullah, the Northern Alliance foreign minister, who like many Afghans uses only one name, had said Northern Alliance troops would not enter Kabul, both to prevent a devastating street war with the Taliban and to allow Afghans to negotiate a political solution to the war. President Bush had asked the opposition to hold off on seizing the capital until a broad-based government could be formed.

"We should try our best not to enter Kabul," Abdullah had said.

But that was before the Taliban fighters decided to withdraw from the capital rather than wage a battle to defend it. As they left, the Taliban forces took eight foreign aid workers, including two Americans, accused of spreading Christianity in Muslim Afghanistan, witnesses said.

Although the Northern Alliance has advanced rapidly in the north, where the Taliban was effectively an occupation army, it can expect more resistance if it tries to capture southern Afghanistan. By moving south, the Taliban fighters seemed ready to fall back toward the last major Taliban stronghold of Kandahar.

The area around the Taliban spiritual capital is rugged, mountainous terrain littered with caves that are believed to provide hideouts for accused terrorist Osama bin Laden and his al-Qaeda terrorist organization.

Northern Alliance leaders met last night to discuss the next step for organizing a multiethnic coalition government. The alliance is dominated by ethnic minorities from the north - mostly Tajiks, Uzbeks and Hazaras. Many Pashtuns, the country's dominant ethnic group, are worried about a government dominated by minority tribes.

U.N. officials said yesterday that the United Nations hoped to bring together Afghan representatives within days to make arrangements for the Afghan capital. U.N. Secretary-General Kofi Annan told reporters that the United Nations must move quickly to develop a political solution.

Abdullah dismissed suggestions that the United Nations should send in troops to govern Kabul. "The U.N. is not ready to send peacekeepers to Afghanistan for the simple reason that there is no peace to keep," he said.

The United States began its air attacks on the Taliban on Oct. 7 after the rigid Islamic regime refused to turn over bin Laden, who has lived in Afghanistan as a guest for five years and is suspected of being the mastermind in the terrorist attacks against the United States.

Also yesterday, Northern Alliance officials said they captured the ancient city of Herat in western Afghanistan. The city sits on the main road to Kandahar. The claims of Herat's capture could not be confirmed independently.

The opposition captured nearly all the Shamali Plain, north of Kabul, yesterday.

After a night of heavy bombing by U.S. B-52 bombers and smaller warplanes, Northern Alliance ground forces launched their attack about 11 a.m. across the breadth of the front line that stretches across the Shamali Plain, an undulating farming region.

As ranks of troops carrying Kalashnikov rifles and wool blankets on their backs moved into positions behind the Northern Alliance front lines, the guerrillas drove squeaky Russian T-54 and T-62 tanks into the narrow lanes that twist and turn through villages of mud-brick farmhouses.

While several American special-forces soldiers directed the air assaults from the rooftop of a heavily guarded house in Rabat, the planes aimed much of their assault at Taliban positions near Rabat and Bagram, two villages on the west side of the Shamali Plain that are near roads that lead to Kabul.

Northern Alliance commanders were able to predict within minutes when the American assaults would arrive, and as the alliance fighters advanced quickly into Taliban territory, they frantically got on the radio to make sure that the pilots did not fire at the concentrations of friendly troops.

The advance yesterday was aided by mass defections of local Taliban commanders, who delivered entire units to the Northern Alliance as village after village fell without a shot being fired. Radio operators excitedly shouted out the names of villages that changed hands, one after another.

At 9:30 a.m., Almas, the commander of forces in Rabat, spoke on the radio to some Taliban commanders and gave them precise instructions on when to defect and turn their guns on their superiors.

Commanders seemed confident that new Taliban volunteers from Pakistan would not fight once the cannon and the air strikes began.

"Some new soldiers have arrived from Pakistan, but they don't have the morale to fight," said Mohammed Arif, a deputy to Almas.

But there was fierce resistance on some parts of the front by Taliban forces, especially outside Rabat. Even after several air strikes, including a deafening B-52 attack, were directed at Taliban trenches, the defenders still fired back with rocket-propelled grenades and small-arms fire. But the resistance only delayed the inevitable.

No casualty estimates were available. It appeared that many Taliban soldiers had escaped, and the few Taliban bunkers around Rabat contained no bodies.